A question from kinematics - motion in one dimension

Natasha Sehgal Asked:

"A stone is thrown in a vertically upward direction with a velocity of 5m/s. If the acceleration of the stone during its motion is 10m/s^2 in the downward direction , what will be the height attained by the stone and how much time will it take to reach there?"

Answer:

Take,

u=5m/s

a= -10 m/s²

v=0 at the topmost position

S= H_max = ?

The eqn of motion to use
v² - u² = 2aS
Which gives H = 1.25 m
From the eqn
v=u + at
t= 0.5 s